The entreaty followed a devastating insurgent assault on a small base under Brown's command in eastern Afghanistan. More than 300 fighters had attacked the outpost, killing eight of his soldiers. For the first time in his 19-year career, Brown had serious doubts about his future in the military.

The offer came from an insurgent known as Mullah Sadiq, who had been on the U.S. kill-capture list since 2005. Brown assumed that some fighters aligned with Sadiq had taken part in the assault.

Sadiq wanted 50 assault rifles, $20,000 and a promise that U.S. forces would not kill him. In return, he promised to turn against more-radical Taliban insurgents and to begin to work with the Afghan government.

Sadiq's proposition gave Brown a chance, however tentative, to achieve a victory of sorts in his corner of Afghanistan and redeem the loss of his men.

"This has the potential to work," Brown told his commander.

It has become a given within the U.S. military after nearly a decade of grinding battle in Afghanistan and seven years in Iraq that U.S. forces cannot kill their way to victory. Enemies must be persuaded to lay down their weapons through a mix of negotiation and force. Grievances must be understood and wherever possible addressed. These principles are at the core of the military's coming campaign in Kandahar, which U.S officials are touting as the most important battle of the nine-year war.

Brown is a firm believer in this new American way of war, one that has forced him to puzzle through dauntingly complex tribal feuds and to overcome a fractured Afghan government that often prefers to fight enemies, such as Sadiq, rather than cede influence to them.

Brown, 41, has struggled to make sense of Sadiq, who insists on dealing with the Americans solely through intermediaries. Some Afghans describe Sadiq as a religious scholar and brave commander. Others maintain that he is a warlord and extremist.

"The bad guys aren't bad because they were born bad," Brown said from his base in Naray. "What no one ever teaches you is how to get to the bottom of the story. No one ever teaches you to ask, 'Why is Mullah Sadiq the way he is?' "

A stirring speaker

Sadiq grew up in a poor family in Kamdesh district, an isolated valley of about 22,000 people. His parents sent him at an early age to be educated at a free religious school in Pakistan.

A bright student and stirring speaker, Sadiq was tapped as a regional commander in the anti-Soviet insurgency, his brother-in-law said. He fought with Hezb-i-Islami, or HiG, a group led by Gulbuddin Hemkatyar, a hard-line Islamist who served briefly as prime minister during the chaotic years after the Soviet withdrawal.